1. Field of the Invention
The present invention relates, in general, to a heat pump type air conditioning apparatus and, more particularly, to an apparatus for promoting the evaporation of refrigerant sucked into a compressor during the heating operation of the heat pump type air conditioning apparatus.
2. Description of the Prior Art
As is well known to those skilled in the art, in a heat pump type air conditioning apparatus, its room heating cycle utilizes its room cooling cycle in a reverse manner and employs the ambient air as a heat source. Accordingly, during a room heating operation, the evaporation efficiency of its refrigerant is in proportion to the temperature of the ambient air. As a result, when the temperature of the ambient air is low, the room heating capacity of the air conditioning apparatus is insufficient. Many attempts have been made to overcome such a shortcoming.
As an example, Japanese Utility Model Publication No. Sho 49-18927 discloses an air conditioning apparatus in which an outdoor heat exchanger and two indoor heat exchangers are disposed in a refrigeration cycle. This air conditioning apparatus is operated in such a way that during a room cooling operation, one of the indoor heat exchangers is utilized as an evaporator and the remaining one is shut to cool indoor air, while during a room heating operation, the outdoor heat exchanger is utilized as an evaporator and simultaneously the two indoor heat exchangers are all utilized as condensers to heat indoor air. Japanese Unexamined Patent Publication No. Sho 54-45949 discloses an air conditioning apparatus in which a refrigerant heater is disposed in a room heating cycle. The refrigerant heater is utilized as an evaporator only during a room heating operation, so that refrigerant liquid is forcibly evaporated in the refrigerant heater after high temperature and high pressure refrigerant gas compressed in a compressor is condensed and liquefied into the refrigerant liquid in an indoor heat exchanger to heat the room.
However, with regard to the former air conditioning apparatus, since the compressor must be utilized when indoor air is heated in the two indoor heat exchangers functioning as condensers, the capacity of the compressor must be large, thereby increasing its manufacturing and maintenance costs. In addition, since two indoor heat exchangers must be mounted in the interior of a room, a large portion of the room is occupied by the air conditioning apparatus, thereby limiting the utilization of the interior of the room. Furthermore, since frost is deposited on the outdoor heat exchanger when the temperature of the ambient air is low during the room heating operation, the heat transmitting efficiency of the outdoor heat exchanger is reduced, thereby reducing the evaporating efficiency of the refrigerant and, accordingly, causing the capacity of the air conditioning apparatus to be insufficient.
With regard to the latter air conditioning apparatus, it is described that the refrigerant is forcibly evaporated in the refrigerant heater, so its cooling capacity is not reduced and the defrosting of the outdoor heat exchanger is not necessary. However, since the construction of the refrigerant heater is not disclosed in the Publication, it is assumed that the refrigerant heater heats refrigerant using electricity that allows the refrigerant heater to be small and to be easily mounted, thereby increasing the maintenance cost of the air conditioning apparatus.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a heat pump type air conditioning apparatus, which is capable of maintaining superior room heating capacity in such a way that the evaporation of its refrigerant is promoted using a cost-free heating source when the temperature of the ambient air is low.
In order to accomplish the above object, the present invention provides a heat pump type air conditioning apparatus, comprising: a heat pump having a compressor, a four-way valve, an indoor heat exchanger, a pressure reducer for a room cooling operation, another pressure reducer for a room heating operation and an outdoor heat exchanger, the compressor, the four-way valve, the indoor heat exchanger, the pressure reducer for a room cooling operation, the pressure reducer for a room heating operation, the outdoor heat exchanger and the four-way valve being connected one after another in series by means of a first conduit, the four-way valve being additionally connected to the compressor by means of a suction conduit, and two points on a portion of the first conduit directly connecting the outdoor heat exchanger to the four-way valve being additionally connected to each other by means of a second conduit; and a heat piping disposed with its condensing portion situated in front of an ambient air sucking side of the outdoor heat exchanger and its evaporating portion situated in a cost-free heat source.